What degree are you doing? If it's science-based and you are frequently using some mental arithmetic skills, then that is good. If not, then I would recommend a maths brush-up. Nothing too serious: just try and get comfortable, fast and accurate with basic functions like division and multiplication, and also with concepts like vector addition and resolution. Trigonometry (sin, cos, etc.) and earth-related geometry (lat, long, angles, etc) is another important subject.
After you are happy with those building blocks, I would study a subject that interests you. Meteorology doesn't require too much 'practice' once the basic principles are understood and you can relate what you've learned to the actual weather every day. Try to understand the forecasts that you get via the media and have a go at interpreting weather charts whenever you see them.
Or maybe you like principles of flight? Again, once the principles are firmly established, you shouldn't need to worry about forgetting them.
Other subjects that require memorisation of facts and figures, like Air Law, might be best left until you have a time-scale to work towards the exam.
Good luck!